Abstract
The life cycles of plants are characterized by two major life history transitions—germination and the initiation of flowering—the timing of which are important determinants of fitness. Unlike annuals, which make the transition from the vegetative to reproductive phase only once, perennials iterate reproduction in successive years. The floral repressor PERPETUAL FLOWERING 1 (PEP1), an ortholog of FLOWERING LOCUS C, in the alpine perennial Arabis alpina ensures the continuation of vegetative growth after flowering and thereby restricts the duration of the flowering episode. We performed greenhouse and garden experiments to compare flowering phenology, fecundity and seed traits between A. alpina accessions that have a functional PEP1 allele and flower seasonally and pep1 mutants and accessions that carry lesions in PEP1 and flower perpetually. In the garden, perpetual genotypes flower asynchronously and show higher winter mortality than seasonal ones. PEP1 also pleiotropically regulates seed dormancy and longevity in a way that is functionally divergent from FLC. Seeds from perpetual genotypes have shallow dormancy and reduced longevity regardless of whether they after‐ripened in plants grown in the greenhouse or in the experimental garden. These results suggest that perpetual genotypes have higher mortality during winter but compensate by showing higher seedling establishment. Differences in seed traits between seasonal and perpetual genotypes are also coupled with differences in hormone sensitivity and expression of genes involved in hormonal pathways. Our study highlights the existence of pleiotropic regulation of seed traits by hub developmental regulators such as PEP1, suggesting that seed and flowering traits in perennial plants might be optimized in a coordinated fashion.
Highlights
Plant life cycles are characterized by discrete phase transitions, such as the initiation of reproduction and the germination of seeds
Clerkx, El‐Lithy et al (2004) performed controlled deterioration and natural ageing tests on seeds from the accessions Landsberg erecta (Ler) and Columbia (Col), which have a nonactive and an active FLOWERING LOCUS C (FLC) allele, respectively (Michaels, He, Scortecci, & Amasino, 2003). Both tests revealed that Col had significantly higher seed longevity than Ler. This suggests that FLC expression is associated with higher seed longevity, which agrees with the results we report here for A. alpina
Few models explicitly consider the role played by genetic elements in the regulation of life history traits, or the degree to which trade‐offs can be constrained by pleiotropy
Summary
Plant life cycles are characterized by discrete phase transitions, such as the initiation of reproduction and the germination of seeds. The regulation of flowering in response to a prolonged period of cold (vernalization) is an important phenological trait that differs among annual and perennial Brassicaceae species. We demonstrate that pep mutants and perpetual flowering accessions show lower seed dormancy and longevity, reduced sensitivity to exogenous ABA and altered expression of genes conferring ABA sensitivity, including ABSCISIC ACID INSENSITIVE (ABI) 3 and 5. To our knowledge, this is the first study demonstrating a pleiotropic link between flowering time genes and seed dormancy or longevity has been found in a perennial species
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